Vinyl plastisol-based fishing lines are commercially dominant at present. Vinyl resin requires the addition of liquid plasticizer to achieve flexibility. A typical vinyl plastisol compound composition includes 100 parts vinyl plastisol resin, 60 parts liquid plasticizer, 2 to 3 parts liquid heat stabilizer, and pigment and blowing agent, glass microspheres or the like as may be required for the product desired. One problem with plasticizer usage in fishing line is that over time it exudates causing circumferential cracks and line degradation.
Plasticizer formulation is a critical factor in such lines. Too high a plasticizer loading results in limpness in the line and ineffective casting in tropical settings. Too low a plasticizer level causes rigidity and cumbersome handling in colder environs. Thus vinyl plastisol lines must be specifically formulated and designated for use in either tropical of cold temperature conditions. Chlorine (part of polyvinyl chloride resin) is a toxic ingredient. As is well known, PVC products of any kind are not biodegradable or degradable. Discarding of used or exhausted PVC lines is thus problematic, since they often end up in municipal landfills. Certain organizations have begun to argue for cessation of PVC production altogether since dioxin (a deadly man-made poison) is created during its manufacture and/or incineration. Fisheries advocates are now likewise beginning to take notice of the potential for habitat degradation posed by the use of vinyl plastisol-based fishing lines.
Prior non-vinyl plastisol-based lines have been utilized (see U.S. Pat. Nos. 5,625,976 and 5,879,758, for example). While effective in some applications such as fishing in tropical flats, such lines have not heretofore been altogether adaptable, particularly for demanding dry fly fishing. Furthermore, attempts to use blowing agents in fishing lines (vinyl and non-vinyl based) can in some formulations lead to rough surfaces finishes due to cell size of the foam created during processing.
Buoyant composite fishing lines heretofore known and/or utilized have included lines having a braided or multifilament core (often nylon) with a vinyl plastisol coating, with the coating having microspheroids blended thereinto to promote buoyancy. Line having a core made of fiber know as Kevlar with a polyester urethane coating which is foamed to provide a multiplicity of air pockets to promote buoyancy are also known (see, for example, U.S. Pat. No. 3,043,045 and the article by A. J. Hand appearing in the March 1988 issue of Rod and Reel magazine).
Other two component lines of various types have included those utilizing gelspun polyethylene multi-strand cores. These lines have not been heretofore favored in fishing lines due to the non-polar surface properties of the fiber, such properties not being conducive to chemical bond development leading to coating delamination.
Recently, to account for the poor bond developing qualities of the core, such two component lines have been manufactured in one of two ways. The first, involves a process of coating application at temperatures above the melt temperature of the core, providing an adhesive fused bond between the core and the coating. The second involves coating the core so as to penetrate the core, substantially entirely filling the interstices in the core material with the coating material thereby entraining the individual fibers of the core in the coating.
In both cases, the resulting line, while useful for some purposes, is not particularly well adapted for use in fly fishing lines. This is so because both processes provide a rather stiff, unyielding line, having few of the characteristics desired for fly casting. Moreover, where a braided core is utilized (preferable in fly line over twisted fibers, for example), the finish on such lines, particularly those produced by the high temperature method, is rough with some of the character of the braid exhibited on the finished surface of the line. In any case, the high temperature application of a coating (i.e., above the melt temperature of the core materials) would damage the core in fishing line manufacture, where coating thicknesses and thus processing times are such that exposure of the core to the elevated temperature is more significant than heretofore utilized by such methods.
From the foregoing, it is apparent that a relatively high test, all-weather fly fishing line could be utilized that is durable, retains desired casting, surface and storage characteristics, and that is environmentally responsible.